A Study on Uncertainty in Seismic Design and Method of Analysis

An earthquake is a natural inevitable unpredictable phenomena which takes place when high stresses built in the earth crust, are suddenly released as the crust breaks with a few kilometres from the earth’s surface. The destruction caused on the structure is not only the shaking of structure , but also due to the action of lateral forces on the structure which tend to bend the structure against the ground motion in order to maintain the inertia of rest. The input shaking causes the foundation of a building to oscillate back and forth in a more or less horizontal plane. The building mass has inertia and wants to remain where it is and therefore, lateral forces are exerted on the mass in order to bring it along with the foundation. For analysis purposes, this dynamic action is simplified as a group of horizontal forces that are applied to the structure in proportion to its mass and to the height of the mass above the ground.